Mechanical timer



Dec. 29, 1970 DUNLOP ETAL MECHANICAL T IMER Filed June 23, 1969 PN w mmmN Www W my? R4 z W United States Patent MECHANICAL TIMER Alexander K.Dunlop, St. Paul, and Raymond A. Hogenson, South St. Paul, Minn.,assignors to Minnesota Mining and Manufacturing Company, St. Paul,Minn.,

a corporation of Delaware Filed June 23, 1969, Ser. No. 835,530 Int. Cl.F01h 43/00; F16h /74 U.S. Cl. 743.5 6 Claims ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION This invention relates to a timing mechanismand in one aspect to a mechanical, automatically resettable, inexpensivetiming device for a machine having a driving shaft associated with theoperation to be controlled.

There are many types of timers presently available, most of which areelectronic to provide for incremental charging of a capacitor, ormechanical timers which utilize separate motors in the timer for drivinga cam adjustable upon the shaft to operate a switch, or which operate onthe order of a clock to trip a switch upon the passing of apredetermined time interval. The timers that are known in the prior arthowever, in their commercial form, are quite expensive, and the timersare relatively complex and thus demand the high price.

The timer of the present invention is adjustable to vary the timeinterval as are most timers. The timer of the present invention receivesa driving force from an operating rotatingmember on the machine whetheroperating only in response to energization by the timer or as a normalfunction of the machine. The timer of the present invention isself-resetting, utilizes very few and generally inexpensive parts, andis not readily susceptible to wear and failure of operation.

The present invention comprises an adjustable rotatable 0 knob havinganindicator thereon to indicate the position or setting of the timer. Asecond knob and plunger is axially movable for operating a switchactuator to drive the switch blade or lever from a normally openposition to a normally closed position relative to a switch. The switchlever is positioned for engagement by the plunger and biased to an openposition. Movement of the switch operating plunger of the timer alsoplaces the timer drive mechanism in contact with a driving member tobegin the timing cycle and operates a mechanical lock means to hold theplunger in its second operating position. The drive mechanism comprisesa drive means for rotating the switch operating plunger which causesrotation of the plunger and the depressible or axially movable knobuntil it reaches a position to engage and release the lock means atwhich time the biasing force on the switch blade returns the plunger tothe normal position and the timer drive mechanism is automatically resetto an original start position. The timer is reset by a torsion or clockspring which acts upon the switch actuator to return it to apredetermined rotational position on its axis.

The above invention will be further understood after ice reading thefollowing description which refers to the accompanying drawing wherein:

FIG. 1 is an elevational view of the timer;

FIG. 2 is an end view of the timer partly in section;

FIG. 3 is a fragmentary sectional view corresponding generally to FIG.2; and

FIG. 4 is a plan view partly broken away to show interiorly locatedpieces.

Referring now to the drawing, a mechanical timer 10 is disclosed whichis adapted to be mounted on most any machine and coupled to a drivenshaft 11 of the machine for operation of a timing function of themachine through a switch 12.

The timer includes a frame 13 or mounting bracket for the timer to mountthe timer on the machine. This frame 13 also serves as a mounting forthe switch 12, as a journal for a drive coupling 14 and has a flange 15for journalling and slidably supporting the switch actuating shaft 16.Ears 17 and 19 are formed on the frame 13 to support the same on themachine.

The switch 12 comprises a housing for a sliding switch arm 20 serving toclose two normally open contacts having terminals 24 and 25 uponactuation of the timer and returning under the force of a biasing springshown in dotted lines to the normal open position bridging the contacton the terminal 24 with an open contact having a terminal illustrated at26. Arm 20 also serves to bias the shaft 16 upwardly axially to a normalor first position. It is of course obvious that terminals 24 and 26could perform a machine function in the normally closed circuit positionto indicate expiration of the timed cycle or the terminal 26 and itsassociated contact need not exist. The timer actuating shaft 16 rests onthe switch operating arm 20 at one end and the other end extends throughthe flange 15 and extends axially through an opening in a first knob 22and receives on its extended end a knob or a button 23 which is fixedthereto. The shaft 16 is journalled in flange 15 by a sleeve 28 fixedthereto and extending partially into the center bore of a crown gearmember 29 secured to the shaft 16 by a retaining ring 27. The gear teethon the crown gear 29 extend downwardly and are positioned axially on theshaft 16 at a position above the drive coupling 14 which includes ashaft 30 extending on one side of the frame 13 and having on its otherend a pinion 31 engageable with the crown gear 29.

Positioned on the crown gear 29 on the surface thereof opposite theteeth is an upstanding lug 32 engageable under bias of a torsion spring33, wrapped about the sleeve 26 and having one end fixed relative to thebracket 15 and the other end thereof engaging the lug 32, with adepending stop or arm 34 formed in a fixed position on the plate 15. Thelug 32 and lug 34 are each long enough to be engageable whether thecrown gear 29 0f the timer drive means is in its normal inoperative oroperative position.

Pressure against the button 23 on the upper end of the shaft 16 causesthe same to be depressed against the biasing force urging the switch arm20 of the switch to the upper normal position. The sliding movement ofthe switch arm 20 after the spring force has been overcome causesengagement of the timer to begin a timing cycle. Axial movement of theshaft 16 actuates a releasable retaining or lock means as acircumferential recess or groove around the shaft cooperates with aspring biased pawl or detent.

As may most clearly be seen in FIGS. 2 and 3, the lock means comprises agroove 37 in the shaft 16 and a pawl or detent is supported in the knob22 and movable therewith. The detent is formed by a spring having onearcuate leg 39 engaging the inner curved wall of the knob 22 and agenerally straight arm member 40 which is biased away from the leg 39and will thus, when in aligned position to fall into the groove 37,prevent axial movement of the shaft 16 in either direction. Adiametrical stop formed in the knob 22 limits the movement of the member40 from the member 39. Extending axially from the free end of thenormally straight arm 40 of the spring is a cam follower or release armin the form of a lug 41 positioned for contact with the cam 36. Rotationof the button 23 will cause the cam 36 to engage the lug 41 and movestraight arm member 40 of the spring away from the arcuate leg 39 andout of the groove 37. When the spring leaves the groove, the spring inthe switch 12 will move the shaft 16 axially away from the actuatedposition back to its normal position, during which movement the spring33, as it was wound during rotation of the shaft 16, will unwind androtate the shaft back to the original starting position with the lug 32engaging stop 34.

As the timing cycle begins under the driving motion of the machine shaft11 via the drive coupling 14, the lug 32 is driven peripherally awayfrom the stop 34 against the force of the torsion spring 33. The shaftis held in its depressed timing position by the locking catch or detentwith arm 40 biased into engagement with the groove 37 on the shaft 16within the knob 22. To indicate the expiration or the lapse of the timein the desired cycle this detent must be released permitting returnaxial movement of the shaft 16 from the switch closed position and toseparate gear 29 and pinion 30. To do this, a cam 36 depends from thebutton 23 and is positioned to engage the arm 40 which engages thegroove 37 of the shaft 16. Rotation of the shaft 16 rotates the button23 and cam 36 such that the latter may release the lock means byengaging the lug 41 and camming arm portion 40 out of the groove 37 inthe shaft. When this detent is released by rotation of the cap 23 theshaft is returned axially to its initial position releasing the slide 20on the switch 12 to again open the circuit between the terminals 24 and25.

Adjustment of the knob 22 about the axis of shaft 16 may be definedthrough substantially 360, however its extent of rotation in any onedirection is retarded by a stop identified by the reference numeral 44on the flange 15 and radially projecting a lug on the knob 22. Theposition of the knob 22 determines the position of the lug 41 and thetimed interval.

In operation the timer is energized when the button 23 moves from theposition of FIG. 3 to the position shown in FIG. 2, causing the teeth onthe crown gear 29 to engage the pinion 31, and the straight arm member40 of the detent of the timer spring to snap into the groove 37,arresting the return movement of the shaft and button from its secondoperative position to its first release position. The switch 20 isopened and the pinion 31 drives the crown gear 29 to rotate the shaft 16until the lug 36 of button 23 engages the lug 41 of the spring torelease the shaft. Release of the spring arm member 40 from the groove37 resets the timer by return of the switch 20, upward movement of theshaft 1-6 and crown gear, and return of the shaft with lug 32 engagingthe stop 34.

Having thus described my invention, what is claimed 1. A mechanicaltimer operative to energize a circuit and maintain the same energizedfor a predetermined time interval which upon lapse of the interval willopen position, biasing means urging said shaft axially toward said firstposition,

releasable lock means for holding said shaft in said second position,

switch means operative upon movement of the shaft to close and open acircuit,

drive means for. rotating said shaft about its axis upon movementof saidshaft from said first position toward said second position, and

cam means operative upon rotational movement of said shaft to releasesaid lock means and disengage said drive means by the return said shaftto said first position by said biasing means.

2. The mechanical timer of claim 1 wherein spring and stop means areprovided for determining an initial rotational position of said shaftand for returning said shaft to said position upon disengagement of saiddrive means.

3. The mechanical timer of claim 2 wherein said releasable lock meanscomprises detent means engageable with said shaft means upon movementfrom said first position to said second position to hold said shaft insaid second position and cooperating with said cam means for releasingsaid shaft from said second position.

4. The mechanical timer of claim 3 wherein said detent means areadjustable relative to the cam means to vary the spacing therebetweensuch that the interval of time may be adjusted at which said timer isreleased.

5. A mechanical timer operative to energize a circuit and maintain thesame energized for a predetermined time interval which upon lapse of theinterval will open the circuit and automatically reset the timer, saidtimer comprising a frame,

a vertically movable shaft supported on the frame for axial movementfrom a first position to a second position, said shaft having a recessformed therein,

an adjustable knob rotatably supported about said shaft and carryingdetent means for cooperation with said recess on said shaft for holdingsaid shaft in said second position,

switch means engaged by said shaft and operative upon movement of theshaft to close and open a circuit, said switch means including biasingmeans normally urging said shaft toward said first position,

drive means for rotating said shaft about its axis upon movement of saidshaft from said first position toward said second position, and

a button secured to said shaft and positioned within said knob, saidbutton having cam means operative upon rotational movement of said shaftwhen in said second position engageable with said detent means torelease said detent means and disengage said drive means affording thereturn of said shaft to said first position.

6. The mechanical timer of claim 5 wherein spring and stop means areprovided for determining an initial rotational position of said shaft onsaid frame and for returning said shaft to said position upondisengagement of said drive means.

References Cited UNITED STATES PATENTS 2,706,224 4/1955 White 200393,388,602 6/1968 Shopsky 743.5

MILTON KAUFMAN, Primary Examiner US. Cl. X.R. 200-39

